I see your colleague Joe already contacted our support department. The best way to get to the bottom of this would be to follow my colleague's instructions, step by step. I'll try to get attention of our level 2 department to this ticket, since the issue looks unusual.

Please escalate. We followed the instructions and we responded last night but have not heard anything. This is crucial.

One of our engineers is already in the remote session, as far as I'm aware, the ticket will be escalated after that.

Matt, please help - our engineer got a restore started, now it failed and she is out of the office and says it will be tomorrow until we hear back...we can't wait that long, this customer has been waiting since Monday. Can you please get us a Level 2 engineer to work with us to finish this up? we just need to get this restore working

The issue has already been escalated to level 2. Writing this message while literally sitting near the guys who are in the remote session either with you or with your colleagues. This seems to be a quite unique issue, so I suggest to continue communication with the techs.

A quick update on the issue.
Here's what was found:
1) The disk where the backups have been stored died(hardware failure) and data was restored using third-party data restoration tool.
2) During disk restoration using that third-party tool it corrupted encryption headers of our backup files, making them unrecoverable. There's also a chance that they were simply corrupted during the disk failure, we'll never know at this point.

For some reason that crucial part of the problem was not mentioned neither by you or your colleagues initially, but we finally got to the root of the issue.
Even though our software is not at fault here, we'll do everything in our powers to restore your data.

To avoid problems like that we recommend using cloud backups along with the local ones, so that if you are faced with a hardware failure the files can always be recovered from the cloud.